Telephone trunking system.



No. 853,682. 'PA'I'ENTBD'MAY 14, 1967.

' W. W. DEAN. TELEPHONE TRUNKING SYSTEM,

-APPLIOATION FILED JUNE 28.1802.

PATENTED MAY 14, 1907;

w. w. DEAN. TELEPHONE TRUNKING SYSTEM.

3 SHEETS-SHEET 2.

APPLICATION HLBD JUNE 28.1902.

' PATENTED MAY 14, 1907.

w. W. DEAN. TELEPHONE TRUNKING SYSTEM.

APPLIOATION FILED JUNE 28.1902. 7

3 SHEETS-SHEET 3,

- W WEMQM- nnrrnn s 'ra'rns.

PATENT OFFIQE WILLIAM w. DEAN, or CHICAGO, ILLINOIS, ASS'IGNOR To KELLOGG SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, IL INoIs, A

CORPORATION OF ILLINOIS.

To all whom it may concern:

Be it known that I, WILLIAM W. DEAN, a citizen of the United States,'residing at'Chicago, in the county of Cook and State of Illinois, have invented new and useful Improvements in Telephone Trunking Systems, of which the following is a specification.

My invention relates primarily to telephone trunk circuits and apparatus co-operating therewith, whereby telephone subscribers whose lines terminate at different central oflices or central stations may be connected together for conversational purposes.

In common battery telephone systems there are two distinct and well defined types of circuits employed. In both types the subscribers lines are each provided at the central oflice with a line signal controlling electro-magnet and a connectionto the common battery, whereby when a subscriber desires to call the central office, he closes the limbs of his line together at his station, preferably by taking up his receiver, thus completing the circuit of the battery through said electro' magnet to operate the same and indicate a call. The limbs of the line are also carried through the normally closed contacts of a relay, known as the cut-off relay, at the central station, which relay when operated servesto open the line to the said electro-magnet and battery to render the line signal inoperative. In one type of circuits the Winding of this cut-off relay is entirely free from and unconnected with the line circuit, and since it is .desired to operate the said. relay only during a connection with the line for conversational purposes, the said winding is included in a eral jacks are connected together. contacts with their connections are entirely -1nade use of for testing or idle condition of theline, since they are local circuit which is adapted to be closed in registering contacts of the line jack or connection terminal and the, plug of the operators cord circuit, when the plug is inserted in the jack to establish a connection with the line. As the cut-off relay must be capable of operation from anx'section of a multiple switchboard these extra contacts in the sev- These isolated from the line circuit proper and are to determine the busy connected directly with battery during an established connection through themedium of a third strand inatheif-cord circuit.v The;

tage of the latter type and the reductipn' in TELEPHONE Tnuuxme. SYSTEM.

supervisory signal associated with eachend of the cord circuit is usually included in this third 'strand'and is shunted during connection by a relay in one of the main strands of the cord circuit. cuits, it is apparent; requires 'a third wire throughout the switchboard for every line; a

This arrangement of cir- Patented May 14, 1997.

third contact or point in every jack, 2. third contact for every connecting plu and a third strand in every cord circuit. t is this characteristic that has-g ven rise to, the pop-- ular yet expressive terms three wire systems three-point jacks and plugs, and three strand cord circuits to denote systems and apparatus of this t e.

The second and other, distlnctive type of systems referred to, is that in which the cutoff relay is connected with the line and is operated over a portion of the talking circult, as distinct from a local circuit independent of the line, whereby the circuit of said relay is closed through one of the main line terminals of the line jacks when the plug is inserted in the jack. With this arrangement it is seen that but quired for the lines and but two cables or wires extend throughout the switchboard; the plug will have two contacts and the cord circuit may be reduced to two strands. The

supervisory signals are also actuated by cur two point jacks are re-' rent flowing over a portion of the talking circult and rendered inoperative by current over the telephone line when the subscriber responds. In this system, moreover, the busy testingis accom lished on one of the mainline terminals oft e jacks. Aradically difl'erent principle of operation is therefore involved in this so-called two-wire or Dunbar system from that of the threewire system, so far as the operation of the cut-off and supervisory relays and the busy testing is concerned. One practical advana of system is that a single switchboard may have a c pacity of 24,000 or more telephone lines owing to the small plugs and jacks that may be used,

while with the three point jacks and plugs.

the capacity of the board is limited to ai'ar less number of lines. tags is the decreased used in and about the switchboard, the cheapening of the manufactureof the apparatus A second great advanamount ofcopperswire I 5 the cost of installationg 3 freely communicate.

and repairs. is necessary, however, in all systen'is to provide trunk circuits hetwcen exchanges in order that the diil'erent suhserihers whose lines terminate thereat :an Such circuits have already heen devised and patented for the tl'iree wire systems, but so far as l am aware. I am the first to provide a practicaliy and cominereiolh, successful trunking Slyiil-lill [or use between exchanges of the two wire or Dunbar type of circuits; and it is to this suhjectmatter that my present invei'ition primarily relates, my main ohject being to pro vide a. trunking; s ,stem that is adapted for use with. two wire circuits and apparatus, and .in which the whole operation of estahlishing and supervising trunking eoiinections hetwcen exchanges is carried out in the host,

most ss-tisiactory and approved manner,

The :entml oliiee at which the call for a connection originates is known in telephonic parlance as the A or outgoing ol'liee and the trunks so used, as the outgoing trunks, while the oiiice at which the conneetion is completed is known as the B or incoming ollice and the trunks as incoining trunks. These terms are used hereinuii ter. with this meaning.

in accordance with my ii'ivention the A operator answr-irs the call of a subscriber for a conneetion in the regular manner, and upon finding that a suhseriher is Wanted innn other exchange she connects her telephone with the order wire or circuit extending to the B operator at that exchange and orders the desired connection. The B operator desi gnates to the A operator the trunk to he used and at the some time tests the wanted line with the tip of the saline incoming trunk plug. The test is ntoi'natic, that is, the B operator is not reipiiicd to cut in with a listening key in order to make the test, it heing mereiv neer to touch the tip of the plug to the jack ,in Upon hurling the line idle the plug is inserted and the ringing kc v operated to call d suhseriher. The J operator ina plug: of her cord circuit in the jack oi' the trunk dosi nated as soon as she is uotilied h the Ho) .itor. ilhcii the B opera.- ior'l is plunger into the wanted linov the suporvisory Bump in. the calling side ol the Aoperatoihi cord ci ,El't lights and remains lightr g), until the siihscriher responds to his call. 1 ringing lamp Hi the B or incoming end ol ithe lrui'ik also lights and rt-imains lighted uuiii the suhscriher responds. When the suhscriher responds the ringing; lamp at the 13 operators position is extiuguislaid and is locked out so that it cannot again lipht during the coi'uiectii'in, not even when the suhsorihcr hangs up his receiver. The super ris-iorv lamp in the A oprra'tors cord circuit is also ebning 'uished as soon a's ihe suhscrihcrrcspends stated, and again lights when the iigiihscriher replaces his telephone upon the I hook. The A operator is thus charged with supervising the connection alter lllc plv are r p, and receives the tll$(()llll((ftill;1 igual directly l rom lzoth sulzscrihcrs. The li opt-r at or receives a.disconnecting signal only when therioperator hastakcu down tlwi-ouuevt ion at her ollir-e. .\t lhis tiuic the disconnection lampa. the iicud ol' thetrunk is lighted. 'lludisvonocciiug lamp at the ioperalons po. i tion prel'orahly operates also as a guard lamp, thut is, as a lamp to indicate when a. mistake has heen. made, as, when the A operator inserts the plug into a. wrong jack. ii ousy hack and dont answer circuit is pro vided in connection with the incoming trunks wherchy when the desired suhscriher is husv or does not answer, the incoming trunk pix may he inserted in the proper iark lrom which a Gt'HI'OSPOlHliIIQ signal is sent to the waiting suhscriher to inform him of the coin dition of the wanted line. in order to carry out these flliOJS operations l provide in connection with the incoming ends of the trunks Your relays and in addition thereto a. lost relaywhich is prefcralilvcommon to all of the trunks at one position. These relays may he designated as the tip relay, which is logged to ground from the tip side of the circuit: thev sleeve relay, legged from the sleeve side of the circuit through hattenv to ground; the trunk relay, which is connected to the outgoing side d the incoming trunlccircuit and which is preferably of high resistance, and the locking relay, which serves when operated to lock out the ringing lamp during the connection.

The invention also consists of the various coinhinations l'iereinaiter dcscrihed and particularly pointed out in the appended claims.

My ii'ivention is illustrated in the accom- *pan ving drawing, in which the same reference characters designate like parts through out the several views, and in which Figure l a. diagram showing the suhscrihers lines leading to two diiiercnt ii'entral ol'lices and the trunking connections let ween said central olliccs to euahle the suhscrihers to he connected for conversation: Fig. 2 is a diagram of a modilied 'lorm oi trunk; ig. Ii is a similar diagram of a iuodilicuiiou in the trunk hctwcen two stations: hi i. l and 5 are l also modifications of trunk cir ..:its, and Fig. l (5 is aiding-ram ol the hu c hack and don't i answer circuits.

lit'ltlll'lllf to Fig. l L designates one ol the pluralitv oi suhscrihcrs lines terminating at i the ccntralollicc This line extends in two i limhs 2 and 3 from the sulrsi "ihers at iou Al to the said central olliee t where it is titled with suitahlc ausvwriug and multiple jacks or connection terminals .l, J. .\t the suh-- serihens statimi, the usual lclcpliouc instruments are provided, and consists of a transmitler, 4, a receiver, .5, a. ringer or call hell, ti. l and the coiulenscr 7. The switch hook, is i adapted in its normal position and when the receiver is placed thereon, to open the circuit'throu h thetransmitter 4 and receiver 5 ;and to 5056 it through the call bell 6 and condenser 7. A retar ation coil 9 is COD:

. nected at the substation when the hook is raised, in parallel with the receiver 5, and condenser 7, to provide a path transparent .to steady currents but opaque to voice currents. The line conductors 2 and 3 include 1b res'pectivelythe armatures or springs 10 and T1 of the cut-ofl relay, R which is permaneiitly legged to ground from the sleeve contacts i of the jacks J, J The armature or sprin 10 is normally connected with r 5 ground t rough the conductor.12, while the opposite armature 11, isjnormally conne ted with conductor 13 containing the line re ay -R for the line, said conductor leading to the 'liveor ungrounded pole of the central batao, 'ter-yB, the opposite pole of which is grounded. The' line relay R controls through its armatore the circuit of the line signal S. The forward contacts 14 and 15 of the cut-off relay "Rare adapted to connect the jacksand the switchboard section of the line with the-external'line circuit when the said cuteofi relay is energized. This, it is to be understood, is atypical two-wire line circuit and is the particularkind with which I prefer to use my 536 trunk circuits, although I do notwish to so limit the use of the invention in all respects. At the central ofiice C, the usual operators =cord circuit is provided, said cord circuit having-an answering lug'P and a calling plug P '3 5 each being provi ed with a tip contact p and jansleeve contact 1') adapted to register withlike contact surfaces] and j in the jacks of ytheline when the plug is inserted therein.

I Thetipcontacts of the plugs are connected "together'by means of the tip strands t and t of the cord circuit and the interposed condenser 0, While the sleeve contacts are likewise connected by the sleeve strands s and s and 'the interposed "condenser 0 A conductor 1 6 'extends from the grounded pole'of the battery"'B"to the tip strand t and contains the winding of the tip supervisory relay 1 asso- 'ciated with the answering plug P, While the live pole of the battery is connected by E510 means of conductor 17 with 'the answering sleeve strand is and includes the Winding of the sleeve supervisory relay 1' These relays Wand r serve to control the circuit of the supervisory lamp S associated with the a 55- answering plug P, the former relay serving to "normally closesaid circuit of the amp, while the'la'tter relay normally opens the same. ;The battery B is associated with the oppo- H site or calling end of the cord circuit and is do ponnected by conductors 18 and 1 9-with the {tip and'sleeve strands t? and s respectively,

the former conductor including the winding fifth; supervisory relay 1*, while the latter "conductor includes the similar relay These relays serve inka manner similar to the relays'r and r, to control the circuit of the supervisory lamp S associated with the calling lug P v T e relays r and] are conveniently referred to as the tip relays and relays r and r5. as the sleeve relays, since they are connected With and operated by current flowing over the corresponding strands of the cord circuit. The tip strand t of the calling and testing plug P is normally open throu h the extra sprin or movable contact 20 of .t e sleeve relay r ut is ada ted to be closed by the said spring and its 'orward contact 21, when the relay is energized. The back contact 22 of this extra spring. 20 is connected through the medium of conductor 23 with one .side of the high resistance and high 'impedance relay r, known as the test relay,

the other side of which is grounded. The ari mature of this relayis likewise grounded and its forward contact is connected'with the primary winding of the operators induction coil 25 by means of conductor 24. The other end of the said primary winding is connected through the medium of conductor 26 t o'the live pole of'the battery B a retardation coil 27 being included in this circuit. The operators transmitter 28 is joined on one side to conductor 26, intermediate her rimary coil and the coil 27; and on the ot er side through conductor'29 to ground. A condenser c is included in the operators local circuit to facilitate talking andis connected as shown. The secondary winding of her inlamp with the tip strand t of the cord circuit by means of the tip rin 'ng key spring A, the

sleeve contact k of sai key bein connected resistance 26%,. I

A trunk circuit is shown extending between the central offices C and C, said trunk with battery lead 26 through wire 26" andcircuit bein fitted at the out oing end with multiple jac s such'as J and or any numher, and with a retardation coil 34 connected to ground from the sleeve side of the circuit. The trunk extends in two limbs 35 and 36 to the central oflice C where it is provided with suitable means for; testing the condition of the wanted line, for ringing the desired sub scriber, and with signals to enable theoperator to prolperly attend the connection. The tip an s e D terminate at the incoming oflice in the wind-, ings w and w of the repeating coil'W, and

eve trunk conductors '35 and 36 grounded spring 57 of between said windings the trunk relay 1 is connected connected, said relay being of high resistance. The opposite windings w and :w of the repeating coil W are connected with an interposed condenser 0 between the; tip

strand t and the sleeve strand s of the flexible end of the trunk circuit, which strands terminate in the corresponding contacts 7) and p" of the trunk connecting plug P. A tip relay 1" is legged to ground from the tip strand 5- of the trunk circuit by conductor 36 and controls through its spring 37 and forward contact a short circuit composed of conductors 38 and 39 of the high resistance trunk relay 1. A sleeve relay r" is'connected on one side with the live pole of the battery B by means of conductors 40 and 4-1 and on the other side with the sleeve strand s. This incoming end of the trunk circuit is provided with a testing apparatus similar to that described for the cord circuit at the central office 0. The forward portion of the tip strand t" is connected with spring 42 of the sleeve relay r while the other portion is connected with the forward contact of said spring. The back contact of spring is joined by conductor 41-3 with the common high resistance and impedance test relay 1', the opposite terminal of which is grounded. The armature of this ,test relay serves when actuated to round one side of the primary winding of the operators induction coil 44, which winding is connected. on the other side with a conductor 45 containing the resistance and impedance 'coil 46 and joined to conductor 47 leading directly to the live pole of the battery 13. The operators transmitter 48 is in a conductor 49 leading from conductor 45 to ground. 7 A condenser c is con' nected between conductor 49 and the .sid of the primary that is adapted to be grounded. The operator s receiver 50 together with the secondary of her induction coi and condenser c are connected permanently with the order circuit or Wire 33 leading to the central office The forward contact o'l spring 51 of sleeve relay 2*", is connected by conductor 52 with the conductor .40 leading from the live pole of generator B The spring 51, which is normally grounded, is connected by conductor 53 leading to oint 54, and thence by conductor 55 through the ringing lamp S to the normal contact of the rounded armature of locking relay r. T e locking relay r is connected in a conductor 56 extending from point 54 to the forward contact of ti relay r. The forward contact of the 100 'ng relay armature is joined by conductor 58 With-conductor 56 at point 59*. The guard and disconnecting lamp 5'' is connected between the point 54 and the armature of trunk relay 7, t e back contact of which is joined by branch 59 to the each contact of spring 57 of tip relay 1. The forward contact of the trunk. relay 1' is esaeez by conductor 0 with the live p le of the battery B This n oming end of the trunk is equipped for selectively ringing subscribers upon a party line. it comprises the ringing key contacts is", l, and l, t5. placed 7 in the strands of the trunk cord and adapted when actuated to suitably connect the alternating current generator with the plug P. This ringing generator comprises the arnniture 60, the grounded brush (ll, the brush (3 from which the alternating current is din ed through resistance lamp 63 to tip spring 7r", when dcpressei'l, and brush (H iron the split connnutator ring which is adapter.

' a current of negative pulsations :140

to deliver only through lamp 65 to the sleeve he when the key is operated. The sleeve contact oi key Ir when operated connects the sleeve ol the plug to battery load -l7 through resistance coil (56 to maintain the cut-oil rclay oi the line operated during ringing. The subscribcns line shown in connection with this ollice is of the party line type and is connected to subscribers l) and D". The. npparatus at these stations is similar to that at the station. A, and are likewise iinlicated, ex cept that the bell 6 at station I) is coni'iected between the sleeve conductor 3 and ground, while at station l) the bell is connected between the tip conductor 2 and ground. The same type of normally disconnecteil jacks. J, J line relay, R cut-oll' relay R, and the line signals 3 are employed and are designated by the same rel'eroi'ice characters. The battery B furnishes current for the o 1erution of these various relays, and signal Well as for talking.

ll, J, and J, J are respectively "busy back and dont answer jacks associated with the incoming trunks. These circuits are shown more clearly in Fig. 6, and comprise an induction coil 67', having itsprimary in circuit with a rapidly rotating circuit breaker 68 and the battery ll", thisbat tcrv be ing preferably the same batter as B, thhueih shown separately for convenience. The secondary of the induction coil 67 is connected in circuit with the rapid circuit interrupter 69 and the more slowly operating interrupter 70. From interrupter 69 a conductor 71 leads to the tip contacts of busy back jacks J, J, through a 50 ohm resistance. coil 72: while interrupter leads by cmiduclor through resistance coil don't answer jacks. The sleeves of hot 11 sets of jacks are united by conductor 75 with the grounded pole oi the battery. The circuit breaker 68 causes induced currents in the secondary circuits which are interrupted a t short intervals by breaker on and at longer intervals by breaker 70 to cause distinctive tones at the jacks J andtl, Wherchyflvhen a trunk plug is inserted in one or the other inc a corresponding signal is transmitted. to the waiting subscriber.

s, as

In tracing the circuits hereinafter," the lan for pointing out the ath for current om the ive or ungrounde ole of the battery to the ground only will, e followed for convenience, it being understood that the return current will seekthe grounded pole 'of the battery and that the circuit will there'- forebe complete.

"ri 0 eration is as follows: The A subscr ber iesiring a connection with. a subscriber located at another exchange removes his receiver from-the hook and thereby'closes line, through retardation coil 9, and transmitter 4 at the substation, and thence over limb 2 back to the central office and spring 10 of cut-oil relay R through conductor 12 to ground. The line relay R is thus 0p- .erated andcloses the circuit of the signal lamp S to ground from the conductor 13'.

The operator upon seeing the line signal exposed'inserts the answerlng plug P 1nto the answering jack J of the subscribers line and connects her telephone 30 with the cord circuit by depressing the listening key k, k,

to receive the order from the subscriber. The insertion of the plug P closes a circuit through the cut-off relay R from the live pole of the battery B through conductor 17,

sleeve supervisory relay 1'", sleeve strand 8, sleeve contacts 17 and 1' of the plug and jack, thence through the winding 0 off relay R to ground. The operation of this relay disconnects the armatures '10 and 11 from the ground wire 12 and from the battery lead 1&and connects them through the forward contacts -14 and 15 of said armatures to the normally disconnected jacks J, J

The operation of the supervisory relay r over the path just traced serves to close through 'its armature and front contact the circuit of the supervisorysignal S which is associated with; the plug P, but it is prevented from gl owing by the operation of the tip superphone-line and the tip strand of the cord c1rcuitand through the conductor 16 to the grounded, pole of the battery B, as soon as the cut-ofi' relay It is operated. visoryn signal S therefore remains inert while the battery 13'' furnishes current over the metallic telephone line for the operation of the supervisory relays and for conversational purposes. .-'I he operators transmitter .28 is receiving current at this time from the battery B? over the conductor 26 through retardation coil 27, thence through the transthe cut- The super-j mitter 28 and over conductor 29,to ground. When sound waves strike the transmitter 28, the current flowing therethrou h is varied which causes a variation ofthe c arge inthe condenser c and a corresponding surge of current through the primary of her induction coil 25. These induce voice currents in the secondary which are transmitted to the line and the operator is therefore able to converse with the calling subscriber.

Upon learning that a subscriber in the exchange C is desired, the A operator depresses with the order wire or circuit 33 and repeats the number of the wanted subscriber. to the B. operator whose headtelephone is permanently connected with the said order wire. The latter operator designates to-the A opers; ator the trunk to be used for the connection and proceeds to test the condition of the the order key k to connect her-telephone v wanted line with the tip of the plug of the incoming trunk named. If the line is idle no fclick will be received, but if busy the sleeve contacts of the jacks of the line will be connected with the live pole of a battery through the sleeve contact and strand of the inserted plug. A complete circuit will therefore be established from the sleeve contact of the tested jack, which it is assumed is connected with the live pole of the battery,. through the tip of the plug P tip strand i spring 42 and'back contact of sleeve relay 1' conductor 43 through'the common high resistance and impedance test relay or responsive device 1* to ground. This test relay. will therefore operate and ground throu h its armature and'front contact one side of t e. primary of the operators induction coil 44, the other side of which is connected by cone- .ductor 45 through resistance 46 and conduc-..

rod

current in the secondary of the said induce tion coil and produce a click in the receiver 50 of the operators set. The operators re-- ceiver will respond to this click at all times even though the order circuit should be ope'nat the A exchange since the-elec,tro-static capacity of her' circuits and that of the order. circuit is ample for the purpose ofproducing the click.

In the three wire systems where the test circuits are insulated from the subscribers line there is no danger of varying the current flowing in the line to the annoyance of the subscriber, during testing. But in the two wire systems where the testing contacts are connected directly with the talking circuit some means is necessary or at least desirable to prevent noticeably varying the current upon lines connected for conversation when testingtheir condition at other sections of the switchboard. This is accom lished in the circuit described by means 0 the test relay lines are tested a sudden or large variation of currrent I ment described ed by through their instruments. It is apparent that any other suitable test responsive device or indicator than the relay 10 can be employed and that-the o'perators telephone can be used in place olthe same or in the circuit with a retardationcoil, but the arrangeis preferred. This relay is preferably common to all the incoming trunks at one operators position as indicated by the branching lines at 43. Upon finding the line idle the plug 1" is inserted in one of ithe multiple jacks of the wanted suhseribers The A operator having received the numher of the trunk to be used inserts the calling plug P of her cord circuit in the jack J" at .her section of the trunk designated. The insertion of the plug P closes a circuit from the live pole oi the battery B at the A office, through conductor 19, sleeve supervisory relay r, sleeve strand 8 of the cord circuit, sleeve contacts of the plug and jack and through retardation coil 34 to ground. This has the effect of positively operating the sleeve supervisory relay P which attracts its armatures and cuts out the test relay r" and completes the tip strand of the cord circuit through armature and its forward contact 21. The closing of this tip strand permits current-to flow from the battery B over the sleeve strand of the cord circuit the sleeve conduetor36 of the trunk line through the Winding whet the repeating coil W at the B exchange, through trunk relay? and thence through repeating coil winding 10 and over the tip conductor of the trunk back to the A exchange and thence over tip strand :5 of the cord circuit and through conductor 18 containing the winding of tip supervisory relay r to the opposite pole of the battery B The closing of this circuit operates the trunk relay '1', but as the resistance of this relay is very high, sufficient current does not flow through the tip supervisory relay 1'' at the A exchange to operate the same. The supervisory signal S" associated with the calling plug P of the A cord circuit is therefore lightourrent flowing from the live pole of the battery B through conductor 26, the signal lamp S, the armature and forward contact of sleeve supervisory relay r and thence through the armature and back contact of lainp is therefore lighted and remains lighted as hereinafter explained until the response of the called subscriber at the B exchange.

The insertion of the incoming trunk plu l l l l I resistance lamp 65, key k",

nect the line relay It of the line to render the line signal inoperative and to connect the normally disconnected jacks with the limbs of the line extending to the sub stations. The operation of sleeve relay 7"" disconnects the test relay 1"" and closes the tip strand t through the spring 42 and its forward contact and thereby establishes the circuit for conversation. It also completes the circuit of the ringing lamp 8* from the battery B over conductor 40, conductor 52, the forward contact and spring 51 of the sleeve rclay, conductor 53 to point 54-and thence through the ringing lamp S" over conductor 55 through the back contact and armature of locking relay 7' to ground' This lamp is therefore lighted and indicates to the oper ator that'the called subscriber has not removed his telephone from its hook. The operation of the trunk relay 1' at this time opens through its armature and back contact the circuit of the guard and disconnecting lamp S to thereby prevent its operation.

Upon the insertion of the trunk plug 1" the B operator rings the wanted subscriber. If the subscriber I) is the one-desired, the ringing key k 7c is depressed which throws ringing current upon the sleeve strand con nected with the plug P" and operates the subscribers bell over the following path: from ground at the generator 1", brush 6] armature of the generator, brush 64 through thence over the sleeve strand of the cord to the plug P over the sleeve limb 3 of the telephone line to the station D and thence through condenser 7 and hell 6 to ground, the receiver 5 being at this time upon the hook 8 and therefore completing the circuit between the condenser 7 and hell 6. It will be noticed that just previous to the depression of the ringing key k the cut-oil relay R was receiving a negative current through its coils from the battery B. At the instant the ringing key k is depressed this path of current from the battery B is .broken, but a new path is immediately establay R is so constructed to be maintained I n continuous operation. when this negative tip supervisory relay 1* to ground. Th s l pulsating current is troin even momentarily releasing its armatures at the moment the ringing key was depressed. The bell 6 atthe subscribers statiori may be of the ordinary polarized type pulsating source of ringing current;

as the presence of the condenser 7, which is connected directly in the ringing circuit permits the'operation of such a bell from the The tip spring of ringing key 75 is grounded at the generatorg with the tip 1 5' 1 this time to provide a pathto ground for the return current ,if the subscriber should rcspond during ringing. Should the subscriber D be the onedesired the ringing key lcf, k, is depressed which serves to connect strand, of the cord circuit to operate the be D The ringing circuit may be traced as follows: from ground at the generator 9 brush 61, armature winding 60 of the generator, brush 62,"through resistance lamp 63, spring is in the tip strand of the cord-circuit thence over the tip strand and tip conductor 2 of the line to the station D and thence through condenser 7 and normally. closed contacts of the hook 8 andthrough' bell 6 to ground. The bell is thus operated' To maintain the cut-off relay R operated during ringing,

the inner contact of the sleeve spring is connected through a resistance coil 66 with thelbattery lead 47 extending to thelive poleofthe battery B. This prevents the de-energization of cut-off relay R while rin ing.

It is apparent t at the arrangement of the ringing eys is such that either key maybe used to calla subscriber at whose station the apparatus is connected in the manner'shown at A, which shows the arrangement which I by taking up his receiver and thereby closes preferablyv usejwhere but one subscriber is placed upon the line. In this case, the ringlng circuit would be complete over'the subscribers metallic circuit,'the current returning to' the grounded side of the ringing gener-- ator by means of the grounded key k or battery contact of the ringing key 7c.

The subscriberhaving been called responds a path for currentbetween the limbs of his line-from the main battery B over conductors 40 and 41, sleeve strand 8 of the incoming oilice and over tip strand t of the incoming end of the trunk including spring 42 and its end of the trunk line 3 of the telephone 'line, thence through retardation coil 9 and transmitter 4 at the sub-station, thence over limb 2 of the telephone line back to the central at the station a batter B 'to operate the same to thereby oped the circuit of supervisory signal lamp S thus indicatlng to the A operator that the Wanted subscriber has responded to his call and that :the parties are m condition to converse. Althoughthe trunk relay r is now de-6Il.91i gized and its armature engages its'back con.

tact, the guard lamp S is not operatedbecause its circuit-is opened at the back contact and spring 57 of tip relay 7". The closing'of spring 57 of tip relay 1" upon its forward contact, however, completes the circuit ofqthoj locking relay 1" as. follows: from theliveole-of the battery B conductors 40 and'52, 5

ront contact and armature 51. of sleeve relayr, conductor 53 to point 54 thence through the winding of locking relay 1" andpover bonductor 56 to the forward contact of spring 57 of tip relay 1* and to; ground. The loc'kin relay I therefore operates and opens throug its armature and back contact the circuitof and indicates to the operator that the called subscriber has responded to 'his ring. The

closing of the armature of the locking relay 1 'upon its forward contact. com letes a lock ing circuit for said relay from t e oint .59, through conductor 58- the. forwar contact and armature of the'relay to ound. This circuit and relay are therefore 'ocked and the ringing lamp S locked out during the remain-. -der of the connection, and canonly be re leased when the sleeve relay 1' is d'-ener 'gized, which occurs when the plug P is Should the tip and sleeve conpulled out. tact so the plug be crossed when the In -is inserted in a jack and the locking an ot e'r relays o erated, they will be immediately released y the opening ofthe sleeve strand;

the ringing lamp 8, which is extinguished rec in ringing'and' no confusionwould (result therefrom.

swermg end of the A cord circuit theA' subscribe'rs line for talking purposes and for The subscribers are now oonnectedtogether {for conversation' a'nd the superyisory s gnals at both exchanges are extinguished. 'Thi' battery Bisfurnishing current over the a'na,

the operation of the vsupervlsory. relays,.the

B is

ing current over'the "incomnnendb 11 trunk and to the sub station furnishing current .oyer the trunk. inc for the operation of the supervisory relays associated-with the. answering end of the A cord circuit, andtheyjbatteryB is gen tot-furnish current for talking and for the operation of"? I the several relays. The voice currents are I20 transmitted inductivel from the subscribe;

ers line L to the trun "circuit throu htheficondenser c and c in the A cord circurt,-and

from the trunk circuit to the incomin'gend thereofand-the subscribers line connected therewith through the medium of the repeating coil W. The condenser 0 between the windings w and 'w of the repeating; coil at iii . cuit ol the disconnecting signal to groui'id.

ebb

the incoming end of the trunk prevents the flow of steady current therethrough but peninits a free passage of the voice currents.

At the termination of the conversation the subscribers return their receivers to their hooks with the result in the caseot subscriber A that the tip supervisory relay r connected with the A cord circuit de-energizedand closes through its armature and back contact the circuit of the supervisory si nal S thus indicating to the'operator that su:. scriber A has returned his receiver to the hook. VJ hen the subscriber D ha'ngs up his telephone current is cut-oil from the metallic line in the same Way and the tip' relay r is therefore de-cnergized. This serves to open the short circuit about the trunk relay 1. The current must now flow through the trunk relay 1, thus actuating it, but is insufi'icient to maintain the tip relay r in the A cord circuit in an operated condition, which therefore allows its armature to fall back closing the circuit of supervisory signal S which becomes lighted and shows to the A operator that the subscriber D has hung up his receiver; The spring'fi'i of the tip relay 7* the incoming end of the trunk is now closed to conductor 59, but the trunk relay 1- having. operated the circuit of the discnnecting amp S is again opened. The A oporator seeing both signals in her cord circuit exposed withdraws both plugs thus restoring all partsat her-office to normal position. The Withdrawal of the plug P at the A exchange ceprives the trunk relay 1' at the incoming end of the trunk of operating current which is therefore de-energized and permits its ormature to close upon its back contact the cir- S said circuit being traced from the live pole of the battery B to conductors and 52, forward contact and armature 51 of sleeve relay 7", conductor to point 54, thence through disconnecting lamp S armature and back contact of trunk. relay 1, conductor 59 and back contact and armature 57 of tip relay 7- The lighting of this signal indicates to the B operator that the A operator has disconnected her cord circuit from the trunk and that the trunk plug P" should be withdrawn. Upon withdrzm'ing this plug the sleeve relay 7" is'de-oncrgizerl and the circuit oi the signal lamp S is opened at the front contact of its arn'iature 5i. T he op'cning oi" the circuit at this cont: .t opens the locking circuit of the locking relay P, which relay istlierefore do-ener ized and permits its armature to return to normal position. All parts are therefore returned to normal position.

The disconnecting signal serves also as a guard lamp in case the A operator inserts the calling plug 1 of her cord circuit in to a wrong ack for the reason that the trunk rclay oi that trunk will be o 'ieratcd while the through the lamp ssaeez sleeve relay r" is not operated. A circuit will, therefore, be completed from the live pole of the battery'over comluctor 40, the forward contact and armature oi" the trunk relay, S to point 54, thence over conductor 53, armature 51 and back contact of sleeve relay r" to ground. This lamp will therefore glow and will indicate to the B operator that a mistake has been made.

se the wanted sul)scribe1"s line is found busy or in case the subscriber having been called does not respond, the plug P is 7 inserted in one of the jacks J, or J and the corresponding signal'is transmitted to the waiting subscriber.

Upon inserting the plug P in one of the busyback or dont answer jacks, for example one of the rent is provided from the battery B through the sleeve strand of the trunk cord, sleeve contacts of the plug and jackand over conductor to ground. This will serve to opcrate the sleeve relay r to complete the continuity of the tip strand 8 of the trunk cord through its spring 42 and the Front contact. Upon the completion of the strand at this point the tip relay r is provided with current from the live pole of the generator B" through the secondarywinding of the induction coil (57, through circuit breaker 69 and thence over conductor 71 through resistance 72 and the ti) contacts of the jack and plug and over the tip strand and through the re ay 1* to ground. This circuit is interrupted at the breaker 69 so that the relay r is alternately energized and de-cne1gized to correspondingly make and break the short circuit of the runk relay 2" which is therefore simultane ously removed from and inserted in the circult of the outgoing end of the trunk. This causes the intermittent operation of the tip relay 7' in the A cord circuit to ellect the lashing of the supervisory signal S" whereby the A operator is notified that the called subscribors line is busy. The flashing of this light of course corresponds to the rapidity ol the breaking of the circuit at breaker G7 or 70 which indicates to the operator whether the line is busy or does not answer. The sub-- scriber is also notilied by the tone caused in his receiver.

The order circuit 33 as is indicated by the branching lines 33, connects the B operator with several A operators either at the same or dill'crcnt exchanges. The A operator is also provided with a plurality of keys /r" to connect herself with the different B operators. The busy back or dont answer a )paratus is common to the various sections oi the incoming trunk board, as is indicated by the branching lines.

Although -l. have described the method of making connections throiwh the medium of the order circuit, i do not wish to so confine the invention for it is apparent that the A opjacks J", a path for cur.

staesa erator is able by means of her testing apparatus to test the condition of the several trunks -withthe result that the trunk relay r operates and lights the lamp S which lamp has been previously termed the guard lamp, but in this method of operation it would act as a calling signal from the A operator to the B operator. The B operator upon seeing the signal 8, would depress her listening key k, 7c, which would connect her receiver in series with the repeating coil windings w and w", these receiver connections being indicated in dotted lines in Fig; 1.. She is therefore able to communicate with the A operator. The. presence of the condenser 12 shown in dotted lines in parallel with the trunk relay 1*, permits conversation between the operators at this time. Upon learning the desired connection, the B operator completes the same as before described. It will also be understood that had the subscriber A called for a connection with another subscriber in the same exchange, the line of that subscriber would have been tested in the ordinarv man-- I nor by means of the cord plug P and the subscriber would have been called by the ringing generator g.

Fig. 2 shows a modification of my invention in which the relay 1' is ermanently connected directly between tffe conductors 35 and 36 of the trunk line, but the tip relay 1* instead of completing when operated a dead short. circuit about the said relay, closes a sliiunting circuit about the same through its armature 37 and front contact and the conso adjusted that relay 1" does not let go, then ,coil.

the signal circuit may be grounded at 59*. The construction and arrangement is otherwise the same in this figure as in Fig. 1, and

the operation is carried out in the same manner. Further description is therefore considered unnecessary.

Fig. 3 shows the trunk relay 1" connected.

normally. in series with the repeating coil windings w and w between the conductors and 3.6 of the trunk llIlG,'tlllS circuit being completed through the armature 37 and back contact of tip relay 7"". When the tip relay operates, however, upon the response of the called subscriber it opens this path through the trunk relay and completes a path through its armature 37 and front contact directly between the two windings of the repeating The trunk relay is therefore cut out of the circuit and a path for current between conductor 38".

the two sides of the trunk line is completed through the contacts of the tip relay and the Otherwise, the construction, arrangement-and operation'of this figure is the same as in Figs. 1 and 2, and it is therefore not described in detail.

Fig- 4 shows specifically the same trunk circuit provided with condensers between its outgoing and incoming ends to furnish a path for talking currents in place of the repeating coil windmgs of the previous figures. condensers is connected directly between the trunk conductor 35 and the tip strand i of the trunk cord while the condenser 0 is likewise connected between the sleeve conductor 36 of the trunk line and the sleeve strand s of the trunk cord. The tip relay 1" and t e sleeve relay 1"" of the trunk cord are conn cted in the same manner as. before. The trunk relay 1 is connected with the trunk conductors upon the outgoing side of the condensers c and c through retardation coils 80 and 81 whereby it is adapted to be operated by current flowing from the outgoing end of the trunk over the metallic circuit thereof. As in Fig. 1, the tip relay r serves, when operated, to close through its armature 37 and front contact and throu h conductors 38 and 39 the short circuit of the trunk relay whereby the trunk relay is deprived of operatin current and isde-energized. The operation will be ap arent from that heretofore described and is t erefore not specifically set forth.

Fig. 5 shows the employment of condensers in place of the repeating coil in a circuit corresponding to that of Fig. 2. In this case, the condensers c and c" are connected as in Fig. 4, but the trunkrelay r is connected directly and permanently between the conductors 35 and 36 of the trunk line. The branch between the conductors containing the re tardation coils 80 and 81 is normally open through the armature 37 and the front con tact of the tip relay 1". When this relay operates therefore in response to the action of the called subscriber in taking up his telephone, this circuit is closed, and as it is of .low resistance as compared with'the trunk relay, the latter is deprived of current and is de-energized. 1t is apparent that the operation described with reference to Fig. 2 can be repeated here, if the resistance of the coils 80 and 81 are adjusted so that rreceives sufficient current during conversation to keep the same operated. Branch 59* only would then be required. The remainder of the operation is the same as described in reference with the other figures andwill be readily understood.

The ground connections heretofore referred to, it-will be uhderstooc}, may be and in practice usually are one anr the same, or they may be the common office retlurn, although it is found by experience, that it 'is practically necessary to place'a dead ground The dimensions of the relays are not the essence of my invention, I have secured good results with trunk relays of.15,000 ohms resistance, tip and sleeve relays of 100 ohms resistance and locking relays of 500 ohms, while the other parts may be of the usual or desired dimensions. I I v While I have described several iormsand several diflerent ways of carrying out my inve'ntion, I would have it understood that the invention is not so limited, as it is apparent that various changes and substitutions may be made therein and still. come within its sco e and principle. But

- hat I do claim as my invention and desire to secure by Letters Patent is:

1. The combinationwith a trunk line, of a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is adapted to be connected, a

retardation coil legged to ground from one side of the talking circuit established. by the connectionof the cord with the trunk, a supervisory signal associatedwith the cord circuit and placed in operative condition by current flowing through the said retardation coil, and means actuated by the response of athe called subscriber for lowering the resistance between the two limbs of the trunk line and rendering said signal moperative, substantially as describe '2, The combination with a trunk line, of a cord circuit to connect with its outgoing end, and a called subscribers line with which its incoming end is adapted to be connected, a retardation coil legged to ground from one side of the talking circuit established by the v connection'of the cord with the trunk, and a supervisory signal associated with the cord circuit and placed in operative condition by current flowing over one side of the cord circuit and through the retardation coil, said signal being adapted to be placed in an inop erative condition by current flowing over the other side of the cord circuit when the called subscriber responds, substantially as, described.

. 3. The combination with a trunk line, of a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is adapted to be connected, a retardation coil legged to ground from one side of the talking circuit established by the. onnection of the cord with the trunk, a su-' 'pervisory signal associated with the cord andplaced in operative, condition by' current assess flowing over one side of the cord circuit and through the said retardation coil, and a relay actuated. by current flowing over the Othcl side of the cord circuit upon the response of the called subscriber to render said signal inoperative, substantially as described 4. The combination with a trunk line, of a cord circuit to connect with its outgoing end and a called subscribers line with whic its incoming end is adapted to be connected, a retardation coil logged to ground from one side of the talking circuit established by the connection of the cord with the trunk, a relay actuated by current flowing over one side of the cord and through said retardation coil, a supervisory signal associated with said cord circuit placed in operative condition by said relay when actuated, a second relay actuated by current flowing overthe other side of the talking circuit upon the response of the called subscriber to render said signal inoperative, substantially as described' 5. The combination with a trunk line, oi a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is adapted to be connected, at retardation coil legged to ground from one side of the trunk circuit during conversation, a supervisory signal associated with the cord circuit and placed in operative condition by current flowing through the said rctardatimi coil, and means actuated upon the response of the called subscriber f or rendering said sig nal inoperative, substantially as described.

6. The combination with a trunk linc, ol a cord circuit to connect with its outgoing and and a called subscribei"s line with which its incoming end is adapted to be connected, :1- retardation coil permanently logged. to

ground from one side of the trunk circuit, a

supervisory signal associated with the cord circuit and placed in operative condition by current flowing through the said. retardation coil, and means actuated by the response of the called subscriber for rendering said signal inoperative, substantially as described.

7. The conibii'iation with a trunk line, oi a cord circuit to connectwith the outgoing end thereof, and a called subscribens line with which its incoming end is adapted to be connected, a retardation coil legged to ground from one sideot the talking circuit, a supervisory signal associated with the cord circuit and placed in condition to operate by current flowing through said retardation coil when the cord is connected with the trunk, a high resistance device at the opposite end of the trunk in the path of current thercover, and means actuated by the response of the called subscriber for removing said resistance from the trunk circuit to thereby pcrmit an increased flow of current over the same to render said signal inoperative, substantially as described.

8. The combination with a trunk line, of a cord circuit to connect with the outgoing end. thereof, and a called subscribers line with which its incoming end is adapted to be connected, a retardation coil legged to ground from one side of the talking circuit when the cord is connected with the trunk, the testing strand of the cord circuit being normally connected with a hi h resistance testing device, a relay adapte' to be actuated by cur rent flowing over the other strand of the cord circuit and through said retardation coil to the cord circuit bein a and '18.- called subscrihers line with. which its jmoming end is adapted to be connected, a retardation coil legged to ground from one side ofthe talking circuit established by the connection of the cord with the trunk, two

relays one associated with one conductor of the cord circuit and one with the other con ductor, a supervisory signal mutually controlled by said relays, a source of current as 1 sociated with said cord circuit, one strand of normally disconnected froinits relaygand t e otherrelay being actuated by current flowing over the other,

strand of the cord circuit and th gough said retardation coil when connection is made with the trunk, said latter rel ay serving to connect the other side of the cord circuit with its'associated relay, the latter relay being controlled by the called subscriber, substantially as described.

v10. The combination with a trunk line, of a cord circuit to connect withits outgoing end and a calledsubscribers line with which its-incoming end is adapted to be connected,

a retardation coil legged to ground from one side of the; talking circuit established by the connection of the cord with the trunk,- two relays one associated with one conductor of the cord circuit and the other with the other ervisory signal mutually relays, a source of current associated with said cord circuit, one strand of the cord circuit being normall discon nected from its rela and connecte with the high resistance testing device, and the other re ay/being' actuated by current flowing over the other strand of the cord ,circuit and through said'retardation c'oil when the cord is connected with the trunk, said latter relay serving to disconnect the testing device and to connect the other side of the cord with its associated relay, the said latter relay being thereafter controlled the called subscrih er, substantially as described.

11. xT-hecmnbinatim with atrunk line,-of a' cordrcircuit to connect with its' outgoing end and-a called'subseribers line with which its ineomingend is adapted to be connected,

can 11 a retardation coil legged to ground from one side of the talking circuit wien the cord circuit is connected with one end of the trunk, a

supervisory signal associated with the cord circuit and placed in operative condition by current flowing through the said retardation coil when the cord circuit is connected with the trunk, a trunk relay connected with the opposite end of the trunk and actuated by.

current flowing over the same when the cord is connected with the trunk, a signal at said second end of the trunk controlled by said relay, and means for placing saidsupervisory signal in inoperative condition by a current flowing over both sides of the trunk whenthe called for subscrihers telephone is in use, substantially as described.

12. The combination with a trunk line, of a cord circuit to connect with its outgoing end and a called subsc'ribcrs line with which its incoming end is adapted to be connected,

a retardation coil permanently legged to ground from one side of the trunk circuit when the cord circuit is connected with one end of the trunk, a supervisory signal associated with the cord circuit and placed in operative condition by current flowing through said retardation coil when the cord. is connected with the trunk, a trunk relay connected with the other end of the trunk and actuated by current flowing-over the same when the cord is connected with the trunk,

asi nal at said second end of the trunk controlled by said relay, and means for placing the said supervisory signal in inoperative con-- dition by current flowing over both sides of the trunk when the called suhsoribers telephone is in use, substantially as described.

13. The combination with a trunk line, of

.a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is adapted tobe connected,

a retardation coil legged to ground from one side of the talking circuit when the cord circuit is'connected with one end of the trunk,

a supervisory signal associated with the cord circuit and placed in operative condition by;

current flowing through the said. retardation coil when the cord is connected with the trunk, a trunk relay connected with the other end of the trunk and actuated by current flowin over'the same side of the trunk circuit with which the retardation coil. 's con- ICO nected when the cord is connected witlnthe I trunk, a signal at said second and meansfor plac-' ing said supervisory. signal in inoperative condition by'current flowing over both sides of the trunk when the called subscribers telephone is in use, substantially as described.

14. The combination with a trunk line, of acord circuit to connect with its outgoing end and a called subscribers line with which its"1ncon1ing end is adapted to be connected,

a retardation coil legged to ground from one iZO adapted to be actuated by side of the talking circuit when the cord circuit is connected to one end of the trunk, a

supervisory signal associated with the cord circuit and placed in operative condition current flowing through said retardation coil when the cord circuit is connected with the trunk, a high resistance trunk relay connected between the trunk conductors and current flowing over the metallic trunk line when the cord is connected with the trunk, a signal adapted to be actuated by said relay, and means for placing said supervisory signal in incperatiye condition by the increased How of eurrent in said trunk when the high resistance ofthe said relay is removed therefrom, substantially as described.

15. T he combination with a trunk linei ol a cord circuit to connect with its outgoing end and a called subscribers line with which 1 its incoming end is adapted to be connected,

a retardation coil legged to ground-tron), one side or the talking circuit when the cord circuit is connected with one end of the trunk, a supervisory signal associated with the cord circuit and placed in operative condition by current flowing through the retardation coil when the cord is connected with the trunk,-

a high resistance trunkrelay connected at the other end of the trunk between the trunk conductors and adapted to be actuated by currcntflovving over the metallic trunk line when the cord is connected with the trunk and the called subscribers telephone is not in use, a signal controlled by said relay, and means actuated when the called subscribers Y telephone is in use for removing the high resistance of said relay from the circuit to permit an increased flow of currentin the signal in-- 16. The combination with a trunk line, of"

the cord is connected with the trunk, alhig'h. resistance trunk relay connected with the trunk at its opposite end and actuated by.

current flowing over the trunk when aco'rifl.

is connected therewith and the ,called sub-- scribers telephone isnot in use, a signal rendered inert by said trunk relay when energized, and ance relay upon the response of the'called subscriber whereby an increased how of current inthe trunk renders said supervisory signal inoperative, substantiall as described. 17. The combination with a trunk line, of

a cord circuit to connectwith its outgoing retardation coil. l;

- ditioiial relay connected with the tip side of .thetrunk relay and when the called subend and a its lllCOlfllilgCDl'l is trimmed to be r: a retardation coil logged to ground ron one -cuit is connected with the tron 'ai1d plabed in operative condition by cur flowing through said retardation coil nl relay connected at the incomin end of means to shunt said high resist' with, a second relay connected with the tr ssaese end and a called suhscribcns line with which it incoming end adapted to be connected, a'retardaticn coil legged to ground froi'n onev side of the tall ting circuit, a supci'risoer signal associated with the cord circuit, and adapted to he placed in operative emulition by current llowing through the retardation coil when the cord is connected with the trunk, a trunk relay connected with the opposite end of the trunk and actuated by can rent flowing thcrcover before the response of the called subscriber, a signal controlled thereby, a supervisory relay assoeiuled \(il h the cord circuit and sign al and adopted actuated to rcmlorthel erinoperotimesupervisory relay being opened by our flowing over the metallic circuit oi the tru oh when it called subscriber responds, substantially as described. 7

12%. The conibinatimi with a trunk lino, oi a cord circuit to connect with its outgoius; end and a called subscribcrs line with which its incoming end is adapted to be connected, god to the sleeve side of the trunk, a supervisory relay :n-zsoct ntrjwl with the sleeve strand ol' the cord circuit, a high resistance trunk rel: U olthe ooowiu: end of the trunk coi rec between the limbs thereof, a sup-e; r1; i'olav cmiuoctod with the tip straodfoi the cord mreui'i, an adthe incoming end oi'thc truul; and :idnnlcd to controlled by the called sulscl'ilwi' when the trunl; is connected o ith the called subscribefs line, whereby when ihe cord circuit connected with the HHiili' the suhl supervisory sleeve relay is a .tuuiod to operate the supervisory signal and the trunk rolay is also actuated but the lip relay does in :t

respond bu reason of the high rrwshlance ol scriber responds the high resistance relay is shunted. to pernnt the operation of the sold tip supervisory relay to thereby render the su- 'iervisory signal ino 'mrotiw, subwuuially as desc ibed,

19. The combination with a uh line, of

i ll oadgoi called subscr :ers hue ilh wl cord circuit to cci'm ct \ru' side of the talking circuit when th cord vira supervisory signal associated with the cord circuit on the cord is'connected with the ti only, a lion trunk and actuated by current flowing urn: the trunk when the cord is connected lllli oz, n:

saacez 33 visory signal associated with the cord circuit at the outgoing end of the trunk inoperative, substantially as described.

20. Tim combination with a trunk line, of a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is adapted to be connected, a retardation. coil legged to ground from one side of the talking circuit when the cord cir cuit is connected with the trunk, a supervisor-y signal associated with the cord circuit and placed in operative condition by current flowing through said retardation coil when the cord is connected with the trunk, a high resistance trunk relay connected at the iii-- coming end of the trunk and actuated. by current flowing over the trunk when a cord 13 connected .therewith and. before the' sub-- scriber has responded, and a second relay at said incoming end actuated upon the respouse of the called subscriber to shunt the high resistance trunk relay to permit an increased. flow of current 111 the trunk and thereby render said supervisory signal at theoutgoing end. inoperative, substantially as described.

21. The combination with a trunk line, of a cord circuitto connect with its outgoing end and a called subscribers line with. which its incoming end is adapted to be connected, a supervisory signal assoclated with the cord circuit and (placed in operative condition when the cor is connected with the trunk, a trunk relay at the other end of the trunk actuated when the cord is first connected with the trunk by current over one side of the same with suitable return, a trunk signal operated by the actuation of said relaya one, a second relay associated with the incoming end of the trunk actuated by current flowing over, a part of the talking circuit when connection is 'made with the called line, said relay when thus operated bein adapted to prevent the actuation of sai trunk signal, and means under the control of the called subscriber for extinguishing said supervisory signal associated with thecord circuit at the outgoing end of the trunk, substantially as described.

22. The combnation with a trunk line, of

' a cord circuit to-connect with its outgoing of the called subscriber to shunt said high resistance trunk relay and thus ermit an increased flow of current over t e' trunk to render said supervisory signal inoperative, substantially as described.

23. The combination with a trunk line, of

a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is connected, a ringing signal for the incoming end. of the trunk, a relay actuated by current flowing over. a part of the talking circuit including one of the jacks of the called subscribers line to direct current 'throughsaid signal to operate the same when the subscriber has been calledbut before his res onse, a second'relay adapted to deprive sai signal of operating current when the subscriber res onds, and means for locking out said signal uring the remainder of the connection, substantially as described.

24. The combination with a trunk line, of a cord circuit to connect with its outgoing'end and a called -subscribers line with which its incoming. end is connected, a ringing signal for the incoming end of the trunk, a relay actuated by current flowing over a part ofthe talking circuit including one of the jacks of the called subscribersline to direct current through said signal to operate the same when the subscriber has been called but before his response, a second relay adapted to deprive said signal of operatin current when the subscriber responds, an means actuated by said second relay for looking out said signal during the remainder of the connection,-substantiall as described.

25. T e combination with a trunk line, of

'a cord circuit to connect with its outgoing end and a called subscribers line with which.

its incoming end is connected, a ringing signal for the incoming end of the trunk, a relay actuated by current flowing over a part of the talking circuit including one of the jacks of the called subscribers line to direct cur rent through said signal to operate the same when the subscriber has been called but before his res onse, a second relay adapted to deprive sai signal of operating current when" the subscriber responds, and means first actuated b said second relay and thereaftercontrolled ay said first relay for looking out said signal, substantially as described.

26. The combination with a trunk line, of a cord circuit to connect withits outgoing end and a called subscribers line with which its incoming end is connected, a ringing sig nal for theincoming end of the trunk, a relay adapted to direct current through said signal to operate the same when the subscriber has been called bu'tbefore his response, a second 'relay responsive to current in the called subscribers line when the subscriber responds, the windings of said relay being out of the path of the voice currents, alocking relay to render said signal inoperative having its cirits incoming end is connected with one side of the trunk and signal, a second relay connected with the subscriber responds, a locking relay to render completed at one point through contacts of a cord circuit to connect with its outgoing cuit initially completed by both said relays and thereafter controlled by the lirst named relay, substantially as described.

27. The combination with a trunk line, of a cord circuit to connect with its outgoing end and a called suhscribers line with which connected, a ringing signal for the incoming end of the trunk, a relay actuated bycurrentdlowing over a part oi the talking circuit including one of the jacks of the called subscril: ers line to direct current through said signal to operate the same when the subscribrn' has been called but before his response, a second relay responsive to current in the called subscribens line when the subscriber responds and having its coil out of the path of the voice currents, a looking relay to render said signal inoperative having its circuit initially completed by both said relays and thereafter controlled by the first named relay, substantially as described.

-28. The combination with a trunk line, of a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is connected, a ringing sig nal for the incoming end of the trunk, a relay actuated upon the connection of the trunk with the called subscribers line, said relay serving to direct current through the ringing other side of the trunk and adapted to respond to current in the metallic line when the and maintain the said signal. inoperative, the crrcult of said locking relay being initially the second relay and thereafter through contacts of the first named relay, substantially as described. I

" 29. The combination with a trunk line, of

end and a called subscribers line with. which its incoming end is connected, a ringing signal for the incoming end of the trunk, a relay connected with one side of the trunk and actuated over a part of the talking circuit upon the connection of the trunk with the called subscribers line, said relay serving to direct current through the ringing signal, a second relay connected with the other side of the t unk and adapted to respond to current in the metallic line when a subscriberis called, a locking relay to render and maintain the said signal inoperative, the circuit of said locking relay being initially completed at one point through contacts of the second relay and thereafter through contacts of the first named relay, substantially as described.

30. The combination with a trunk line, of a cord circuit to connect with the outgoing end thereof and a called subscribers'line with which its incoming end is connected, a ringing signal for the incoming end of the trunk see c under the control of the operator vfor unlock ing said signal after it has been locked without (lisconru-cting the trunk from the called line, substantially as described.

3]. The combination with a trunk line, of a cord circuit to connect with its outgoing end and a called subscribens line with which its incoming end is connected, a ringing signal for the incoming end of the trunk adapted to be operated when the trunk is connected with the called subscribers line, means for rendering the signal inoperative upon the response of the called subscriber and for locking out the same during the remainder of the connection, and further means whereby should the signal become accidentally locked out when making a connection the same is unlocked during ringing, scribed.

32. The combination with a trunk line, of a cord circuit to connect with its outgoing end and a called subscribers line with which its incoming end is connected, a ringing signal for the incoming end of the trunk adapted to be operated when the trunk is connected with the called subscribens line, a

relay for rendering said signal inoperative upon the response of the called subscriber, a second relay tor maintaining the first named relay in operative condition during the connection, a looking out circuit for said signal closed initially at one point by the first relay and thereafter maintained closed by the second relay, a ringing key adapted to connect the ringing generator with the called subscribers line, means for opening the circuit of said second relay by means of the.

ringing key when the subscriber is being called, whereby should it become necessary for the operator to again ring the subscriber,

the signal will be unlocked, substantially as deseri bed.

substantially as derob 33. The combination with a trunk line, of i a cord circuit to connect with its outgoing end and a called subscribens line with which its incoming end is connected, a ringing sig nal for the incoming end of the trunk, a relay actuated over a part of the talking circuit and adapted to direct current through said signal to operate the same when the subscriber has been called but before his-response, a second relay adapted to deprive said signal of operatingcurrent when the subscriber responds, and means first actuated by said secondrelay and thereafter controlled by said '[irst relay for locking out said signal, and a ringing key adapted to open said portion of the talking circuit and to connect the ringing assess generator with the called subscribers line whereby the signal will be unlocked during ringing, substantially as described.

34. The combination with a trunk line, of

'a cord circuit to connect with its outgoing and further means operated by and during the connection of said cord circuit with the trunk for rendering said signal inoperative,

substantially as described.

35. The combination with a trunk line, of

' a 'cord circuit to connect with its outgoing end and a called subscribers line having onl two wires extendinthroughout the mui tiple switchboard with which its incoming end is connected, a disconnect signal for said incoming end, means 0 erated by current flowing over a portion oi the talking circuit when connection is made with the called line for placing said signal in condition to 0p disconnected from the trunk, substantially as described.

36. The combination with a trunk line, of a cord circuit to connect with its outgoin end and a called subscribers line with whic its incoming end is adapted to be connected, a signal associated with said incoming end, a single coil relay normally bridged across the incoming end adapted to beoperated by current sent over the trunk circuit, a second relay at'said incoming end adapted to be 0 er-- ated by current flowing over a portion 0 the talking circuit andhaving its coil out of the path of the voice currents, said relays jointly controlling said signal so as to operate the same to give a guard indication when the cord circuit is connected with the trunk circult'and the trunk circuit 18 disconnected from-the said line or toplacc said signal in condition to operate so as to give a disconnect indication when the cord circuit is disconnected from the trunk and the trunk is connected with said line, substantially as described I 37. The combination with'a trunk line, of a cord circuit to connect with its outgoing end and a called subscribers line having only two wires extending throughout the multi le switchboard with which its incoming enc is connected, a disconnect signal for said incoinjug end, means actuated by current flowing over a part of the talking circuit when connection is established with the called line for point to place it in condition to operataand controlling the circuit oli said signal at one .iurther means operated by theconnection of said cord circuit with the trunlrior controlling the circuit of said signal at another point rendering the same inoperative, substantially as described. 4

38. The combination with a 'trunk line, of

a cord circuit to connect with .its'putgoing end and it called subscribers line having only two wires extending throughout the multi le switchboard with which its inoomin en 18 connected, a disconnect signal for sai income ing end, ,a relay actuated by current flowing over a portion of the talking circuit for PIILG.

ing said signal in. condition to o erate,a-nd.a'

trunk relay at the incoming en of the trunk to be actuated by thc'connection of the cord circuit with the trunk, the energization of switchboard with which its incoming end is.

connected, a disconnect signal for said incoming end, arelay actuated-over a portion of the talking circuitwhen connection is-made;

with a called line for closing the circuit of said'{ signal a one P nd'a trunk relay n; th incoming end of the trunk actuated bycurrent from the cord-circuit when the cordIis connected with the trunk, said truhk relay serving when energized to open the circuit of' I the said signal, substantially as described, T

40. The'combination with a trunk line, of

a cord circuit to connect with its outgoing end and a called subscribers line havingonly two wires extending throughout the multi lo switchboard with which its incomin' en is' connected,-a disconnect signal for sai incommg end placed incondition to o erate by 01313 rent flowing over a portion or t e talking 011- cuit when the trunk'is connected with the V called line, and means depending upon the connection of the cord with the trunk toprevent the actuation of said signal during such latter connection, substantially as described. 41. The combination with a trunk line, of

acord circuit to connect with its outgoing end and a called subsoribers line having only two wires extending throughout the multi le switchboard with. which its incoming en is connected, a disconnect signal for said incoming end placed in condition to operate by current flowing over a portion of the talking ci'r cuit when connection is established with the called line, and means to prevent the actuation of said signal during such connection 7 either when the cord is connected with the trunk or when the called subscribers tele-1 phone is in use, substantially as described.

42. The combination with a trunk line, of

ing d of the trunk, means operated over on. e ot the linking circuit to direct ourcougd said signa when the trunk is with the called line, a. trunk relay else at th incoming end of the trunk and zictouted when the cord circuit is connected witli the trunk, the said trunk reloy serving to render the signal inert when the cord is connected with the trunk and to operate the same whenthe cord circuit is discomiected, substantially as described.

&3. The combination with a. trunk line, oi.

circuit to connectwitb. its outgoing and it called subscriber's line with which incoming end is connected, a disconnect signal ror sold incon'iing end placed in conditiozr. to operate by current flowing over a portion ol" the talking circuit when connection is made with the called line, it relay at the incoming end of the trunk actuated by current thcrcover when the cord circuit is connected with the out oing end, at second relny s t the incoming end of the trunk responsive to current in the line T-Illfili the called subscriber answers, said signal being rendered inert during such connection by the encrgimtion of cl. r or said relays, substmitinlly es described. I

H. The combination with a trunk line, of o' cord circuit to connect with its outgoii'ig end and r1 celled subscribers line with which its incoming cud is connected, a. disconnect signal for the incoming end of the trunk, a relay actuated by current flowing over it pert ol the talking circuit when the incoming end of the t it: is connected with the called subscriber circuit. ol said 81 url at one point, a. second rehty connected wlh the incoming end and con-trolling said circuit atouothcr point and adapted to be actuated when the called subscriber rcsrmnds, a trunk relay connected with the outgoing end oil the trunk and octib :riicd by current over and between the two limbs ol' the trunk line, and means whereby said signal is actuated when the first named rclz'ty is actuated and the other two relays are dc-cnergized, substantially as described.

453. *lhc combination with o trunk lllld, of o cord circuit to connect with its outgoing end and e called subscribcus line with which its incoming end'is connected, it disconnect signal at the incoming end of the trunk, o v actuated when the incoming end of cormcctcd with the cullcrl subline to direct current through soid discm'inectsignal, a trunk rclzry at said lnooming' end connectwl with the outgoing cud ol the trunk and. actuated by current tbercovcr s line said relay controlling the when the cord circuit is connected with the 05 trunlr, a third relay connected with the incoming end of the trunk and actuated when the subscriber responds, said signed being rendered inoperative by the operation of either of the trunk relays or the third relay and rendered operative during the connection by the de-energizetion of said two rclovs, substantially as described. i

do The combination with it trunk line, of a cord circuit to connect with its outgoing 7 5 end and it called subscriber's line with which its incoming end is connected, a disconnect signal at the incoming end of the trunk, it relay actuated over a portion of the talking circuitwhen connection is made with a. line So to direct current through said signal, a trunk relay connected with the outgoing end of the trunk and actuated by ciu'rent therecvcr when the cord circuit; is connected with the trunk and the called subscribors telephone 8 5 is not in use, it third relziy connected with the incoming end of the trunk and actuated when the subscriber responds, said signal being rendered inoperative bythe operation of either the trunk relay or the third relo and operative by the dc-cnergizution 0]" said two relays, substantially as described.

47, The combination with :r trunk line, ol a cord circuit to connect with its outgoing end and 21 called subscribefls line with which its incoming end is adapted to be connected, it guard signal for the incoming end of the trunk, menus to actuate said signal by current sent over the two limbs of the trunk line in series when the cord circuit is connected. ion with the trunk and further means actuated by current sent over n. portion of the talking circuit when the trunk is connected with it called' line for rendering said signal inert, substantially {LS described. it

48. The combination with a trunk line, of a. cord circuit to connect with its outgoing end and it called subscribers line with which its incoming and is adapted to be connected,

n guard signal for the incoming end ol the no trunk, a. relay controlling the circuit of said signal at one point and adopted to be nctu. etod over a portion ol the talking circuit when the incoming end 01'' the trunk is connected with the called subscribers line and n5 having its c il out of the path of the voice currents, 2L trunk relay cormectod with the outgoing end of the trunk and adapted to be ulctuated by current llowinq over and betwcen the two limbs thereo when the cord 12o circuit is connected with the trunk and controlling the circuit of said signal at osccond point, and means for actuating said signal when the first named relay is (lo-energized and the trunk relay is energized, substuutiully as described. V

ll). The combinetion with a trunk line, ol u cord circuit to connect with its outgoing second relay connected with end of the end and it called subscribers line with which its incoming and adapted to be connected, a signal for the incoming end of the trunk, a relay connected at the incoming end of the trunk with the outgoing end and actuated. by current thereover from the cord circuit, a the incoming trunk and actuated when the trunk is COIU)QCi7(-(l. with the called sub scribers line, a third. re at the incoming end of the trunk responsive to current in the line when the subscriber answers his call the 7 said signal being actuated at dillercnt times by currei'it over two dillicrent paths, one of said paths being closed when the second rclay is energized and. the first and third relays (lo-energized and the other path being closed when the first relay '3 energized and the second relay is de-cni'irg ized, whereby in the first i as nice it serves a disconnectii'ig sic nal and in the second as a guard signal, substantially as described.

50. 'l. he combination with a trunk line, of a cord circuit:- to connect with. its outgoing end and a called subscribers line with which its incoming endis adapted to be connected, a signal for the incoming end ol' the trunk, a relay connected with the outgoing end of the trunk and actuated by current thcrcover when the incoming end i connected with the called subscribei"s line and when the sub scriberf's telephone not in use, a second relay connected with the incoming end of the trunk and actuated when the trunk is connected with the called subscriber's line, a third relay at the incoming end of the trunk responsive to current in. the line when the Subscriber responds, said signal being adapt- .ed to be actuated over two different paths,

one of said paths including l'orward contacts of the second relay when it energized and normal contacts of the other two relays, and the other path includii'igi the forward con tacts of the first relay when it is energized and normal contacts of the second relay, substantially as dcscri bed.

51-. The combination with trunk line, of a cord circuit to connect with its outgoing end and it called suhscri.bc1"s line with which its incoming end is adapted to be connected, a supervisory signal associated with the cord circuit, a relay at the incoming: end of the trunk actuated over a part of the talking circuit when connection is made with the line, a testing circuit completed through the normal contacts of said relay, a second relay normally not in c'ondition to operate by current flowing over the line, said first named. relay serving, when actuated to sever the test circuit and place said second relay in. condition to respond when the subscriber answers, and means for controlling thesupervisory signal. at the other end of the'trunk b T said second relay, substantially as described associated with 52. The combination with a trunk line, of a cord circuit to connect with' its outgoing end-and a called suhscrihers line with which its incomingend is adapted to be connected, a supervisory signal associated with the cord circuit, .a relay at theiincoming end of the trunk actuated. over a part of one side of the talking circuit, testing circuit from the tip of the trunk plug completed through the normal contact-s oi sai d. relay, a second relay associated with the talking circuit and normally disconnected from the tip, and means for severing the ingthe second relay with the tip and talking circuit when the first named relay is actuated. whereby said second. relay is placed in condition to operate by current in the line whenthcsubscriber responds, and means actuated by said latter relay for controlling said supervisory signal, substantially as described.

53?. In a telephone system, a calling subscribcrs line and a called subscribcrs line, a' cord circuit and trunk to connect said lines together for conversation, a relay associated. with said trunk and adapted to operate over a talking. strand, a. source of distinctive signaling, current with which the incoming end of the trunk may be connected when the called subscriber is busy or fails to answer, means for operating said relay when the trunk is connected with saidsourcc to place the trunk in. condition to respond to the signaling current, whereby the calling subscriber is duly notified of the condition ol' the called line, substantially as described.

54. The combination with a trunk line, of

a cord circuit to connect Withits outgoing .end and a called subscnbers line with which its incoming end isadaptc-d to be connected, a supervisory signal placed in operative condition by current flowing over apart of the talking circuit when the cord is connected with the trunk, a source of distinctive signaling current with which the incoming end of the trunk is connected when the called subscriber is busy or fails to respond, a device the incoming end of the trunk responsive to said signaling current to cause a flow of current over both sides of the trunk to render said supervisory signal inoperative in accordance with the variations of said current, substantially asidesoribed.

55. The combination with a trunk line', of a cord circuit to connect with its outgoing end and a called sul.)scribers line with which its incoming end is adapted to be connected, a supervisory signalassociated with'the cord circuit and actuated byxcurrent flowing over thetrunk when the cord is connected with the trunk, a high resistance device in the path of said current to prevent rendring the supervisory signal inoperative, a source of distinctive signaling current with winch, the

testing circuitand connect-.

incoming end of the trunk is connected when 

